Windley U.S. Pat. No. 3,971,202 describes cobulking electrically conductive sheath-core filaments such as those disclosed in Hull U.S. Pat. No. 3,803,453 with nonconductive filaments to form a crimped, bulky carpet yarn which dissipates static electricity charges which are annoying to people who walk on nonconductive carpets when humidity is low.
De Howitt U.S. Pat. No. 4,612,150 describes introducing spin-oriented electrically conductive bicomponent filaments into a quench chimney wherein nonconductive filaments are melt spun and cooled, combining the conductive and nonconductive filaments at a puller roll, drawing and cobulking the combined yarn and then winding up the yarn. While the above process is an improvement over previous methods of producing antistatic yarns for carpets and other uses, the spinning and winding speed of the conductive bicomponent filaments is often limited to about 1400 yards per minute (ypm) (1281 meters per min.) so that the filaments will not break when they are drawn at the same draw ratio as is required for the nonconductive filaments. Higher spinning speeds produce higher orientation in the conductive filaments which reduces their elongation to break. With lower elongation, occasional filament breaks occur which cause filament wraps in the processing equipment and gaps in the conductive filaments in some portions of the product, thus resulting in reduced productivity, poor static dissipation, and defective or lower quality product.
Brody U.S. Pat. No. 4,518,744 discloses a process of melt spinning a fiber-forming thermoplastic polymer, more particularly polyethylene terephthalate, polyhexamethylene adipamide or polypropylene, at a minimum wind-up speed of 2 kilometers per minute in which there is added to the fiber-forming polymer between 0.1% and 10% by weight of another polymer which is immiscible in a melt of the fiber-forming polymer, such other polymer having a particle size of between 0.5 and 3 microns in the melt of the fiber-forming polymer immediately prior to spinning. Brody also discloses melt spun fibers produced by such a process and in which the other polymer is in the form of microfibrils.